A soluble multienzyme system for DNA replication has been developed from unfertilized eggs of the frog, Xenopus laevis. Supercoiled pXlr DNA molecules (col El based plasmids containing Xenopus laevis ribosomal DNA restriction fragments) are used as templates. DEAE cellulose column fractions were used initially as the replication machinery. The ability of electrophoretically homogenous DNA polymerases alpha, beta, gamma, delta, DNA binding protein, relaxation protein, RNAse H, and RNA polymerase II to substitute for various DE-52 fractions will be assessed. In addition, an attempt will be made to purify I-factor, a protein involved in the initiation of DNA replication during early embryogenesis.